Funds are requested to purchase a single photon counting lifetime instrument, mostly upon the system developed by Photochemical Research Associates. The instrument will be capable of measuring fluorescence lifetimes, time-resolved anisotropies and time-resolved emission spectra. These functions will be under computer control. This will be a multi-user instrument and the main users will be Professors J.R. Lakowicz, G. Inesi, E. Bucci, and R.F. Steiner. In addition, instrument time will be reserved for other researchers. The chosen instrument and components are those found to be widely useful from our own past experience and that of other laboratories. This conservative design was selected in order to provide maximum reliability and minimum confusion for the multiple user. Mostly, the instrument can be purchased as turn-key system. Some minor hardware and software development will be needed to accommodate the scanning monochromators and to automate polarizer rotation and the interchange of samples. Even with the convenience of purchasing an instrument which is ready to operate, this system provides significant measurement capabilities which will enhance the research of these four individuals. The research projects will be as follows: Lakowicz, Dynamic Properties of Proetins and Membranes; Inesi, Properties of Ca-ATPase; Bucci, Effects of Ligation on the Dynamics of Soluble and Membrane-bound Proteins; and Steiner, Interactions of Calmodulin with Proteins. A procedure for time-sharing and payment of service contracts has been agreed upon by the users. The service contracts and maintenance will be equally shared for five years. The instrument will be located in the laboratory of Dr. Lakowicz, adjacent to other fluorescence instrumentation. Since these other instruments are utilized at least provide advice for users of the new instrument.